Signal adjusting antenna



Feb. 20, 1962 D. E. BRINKERHOFF 3,022,420

SIGNAL ADJUSTING ANTENNA Filed Aug. 51, 1960 IN V EN TOR.

3,622,420 SIGNAL ADJUS'HNG ANTENNA Donald E. Brinlrerhoff, Kokomo, Ind., assigner to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Aug. 31, 1960, Ser. No. 53,184

' 4 Claims. (Cl. Z50-20) This invention relates to power driven automatically adjustable antenna means and more particularly to control means for automatically adjusting the eiective antenna length dependent upon the amplitude of the received signal.

Many of the automotive antenna used for car radio receivers are power driven to extend and retract the length of the antenna as the set is used. In vehicular use it is not only purposeless to have the antenna project beyond the contines of the body when the radio receiver is not in use but it is dangerous in that it is much more liable to be damaged if it remains so extended. If the radio antenna is retracted when not in use or not extended any further than absolutely necessary to obtain a satisfactory listenable signal when in use, the antenna will be mechanically protected from damage caused by striking lobjects and also the appearance of the vehicle will generally be improved.

It is, therefore, an object in making this invention to provide means for automatically controlling a power actuated antenna to adjust the same to optimum length dependent upon the strength of incoming signals.

It is a further object in making this invention to provide signal strength controlled means for adjusting the effective length of power driven antenna means.

It is a further object in making this invention to provide a control voltage proportional to the strength of an incoming signal to adjust the effective length of a power driven antenna.

With these and other objects in view which will become apparent as the specification proceeds, my invention will be 'best understood by reference to the following specitcation and claims and the illustrations in the accompanying drawings, in which:

FIGURE 1 is a block diagram of a control system embodying my invention; and,

FIGURE 2 is a circuit diagram of a control system for the motor of a power driven antenna embodying my invention.

While the concepts of vmy invention are broad and encompass any means for automatically adjusting the length of an antenna for satisfactory reception dependent upon received signal strength, as illustrative, the present description will be applied to a type in which the antenna length is adjusted by a reversible electric motor though my invention should not be limited to this type.

' In current commercial types of motor driven antenna small reversible electric motors are provided which run in one direction upon the closing of one control switch to extend the antenna, and reverse and run in the opposite direction upon the closing of another switch to retract the antenna. lf both switches are open the motor remains deenergized and the antenna remains stationary.

FIGURE 1 shows in block diagram form the basic elements that form my invention. In this figure, 2 indicates an extensible telescopic antenna for picking up resultant high frequency signals. A wiping contact 4 engages the antenna to take ofi such signal energy andthis is connected through conductive line 6 to the input of a standard radio receiver 8. The antenna 2 is extended or retracted by a drive motor 10, said drive motor being of thereversible type capable of running in either direction dependent upon the control switching means. A balanced relay control switch 12 is connected to the drive motor through a plurality of conductive lines 14, 16 and 18 to control it to run in either direction, to extend or retract the antenna dependent upon the demands of the relay switching means 12. Within a standard receiver 8 it is possible to develop a direct current voltage which is proportional to the strength of the incoming signals, such as the conventional AVC voltage and this voltage may be tapped oif through line 20 and applied to a DC. amplifier 22 where it is amplied to a usable output value and it is this voltage which controls the operation of a relay 12 to in turn control the driving motor to vary the length of the antenna in proportion to the signal strength.

rthere is a sensitivity control for the D.C. amplifier which has been indicated as a variable resistance 24 connected thereto. By the use of this system when a signal is received on the receiver 8 which is of relatively low amplitude the current system Will call for a further extension of the antenna and the drive motor 10 will be energized to extend the same. As the antenna is extended the strength of the incoming signal together with the strength of the control signal applied by the D C. amplifier will increase until the relay 12 balances at a desired point and the antenna will then cease to move, the motor TJE will be deenergized and the antenna will remain in that position until the incoming signal strength changes. lf the vehicle is driven farther away from the transmitting station the antenna will be gradually raised to obtain the same listenable strength of signal. On the other hand if the station is approached and the signal becomes stronger the antenna will be retracted. At no time will more than the necessary length of antenna be in evidence and the antenna will, therefore, be protected mechanically and the appearance of the car enhanced.

FIGURE 2 shows in detail the circuitry used to control the drive motor lll. In FIGURE 2 the dash rectangular outline 26 illustrates the last IF transformer of the standard receiver S. rthis transformer is provided with the` conventional primary Winding 2S and secondary winding 3d, both of which are tuned to the IF frequency of the set by condensers 32 and 34 connected thereacross. This transformer also includes a tickler coil 36 which picks up the control signal for the antenna motor which it is intended to use. The tickler coil has one terminal connected through a diode 38 to one end of a plurality of resistances 40, 42 and 44 in series to ground. These resistances form a voltage divider across which the control signal is developed and a proportion of which signal is amplified and fed on to the control motor. The opposite terminal of the tickler coil 36 is connected directly to ground. An electrolytic condenser 46 is connected across the potential divider formed of the resistances 40, 42 and d4. A direct current voltage across the condenser is developed by rectification of the signal by the diode. Therefore, as the strength of the incoming signal varies, a variable voltage will be developed across the condenser and the potential divider.

An adjustable tap 48 moves over the surface of resistance Lt2. and is the sensitivity control for the system. This adjustable tap 43 is connected directly to the base electrode Sil of transistor 52. The transistor 52, also has a collector electrode S4 which is connected directly to the base 56 of a second transistor 5S to amplify the output thereof. Base 5d is connected to ground through a bypass condenser 6a. Emitter 62 of the transistor 52 is connected to ground through a biasing resistor 64 and also to a source of power indicated as -jthrough resistance 66. A further biasing resistor d@ is connected between the source of power and the emitters 'iii and 72 of transistors 58 and '74, respectively. Resistances 76, 7S and a variable resistance Si) are connected in series between the power source and ground forming a voltage divider and the base electrode 82 of the transistor 74 is acces-ao connected to a point intermediate resistors and 78 for proper bias.

Referring now to the motor and its immediate control circuit, the drive motor lil, as before mentioned, has three leads connected thereto, one lead 16 extends to the source of power marked plus, the second lead ltextends to a stationary Contact 92 of the balanced relay f2, and the third lead fd extends to a similar spaced stationary contact 28. As before mentioned, the motor is pro vided with a plurality of field windings, the energization of which cause the motor to be driven in opposite directions. The common power lead la is connected to both windings, the leads ld andl lo being independently connected to one or the other winding for completing the grounding energization circuit therefor. Mounted between the two stationary contacts and 92 of the balanced relay l2 is a pivotal conductive armature 5I-'i which is grounded. This armature is so mounted as to ordinarily assume a central position so 'that it not engage either stationary Contact. Mounted adjacent the sarnc and on opposite sides thereof are two operating coils 36 and 55, the energization of either of which causes the armature to rotate about its central pivot and engage one or the other of the stationary contacts or The operating coil 96 of the relay has one end grounded and the other end connected through conductor to the collector electrode ll of transistor iid. A condenser lltlfi is connected between line lilo and ground. in like manner operating coil 9S of. the balanced relay l2 has one terminal grounded and the remaining terminal connected through conductive line lila to collector electrode lli of the transistor 7d. Condenser' llo is connected between conductor lilti and ground.

in the operation it is to be noted that the relay coils eid and 98 tend to rotate armature 9d in opposite directions to control the drive motor, The motor itl will be energized to extend or retract the antenna or will remain in a given position dependent upon coil eucrgization. Assuming that the receiver has been turned on and is operative the operator then adjusts the position of the sensitivity control il to a position which he assumes will give him a satisfactory listenable signal with the proper antenna extension. lf the antenna is extended further than necessary for a given station then the amplitude of the incoming signal induced in the ticlder coil 36 develops a voltage across condenser de and the potential divider including resistance 42, which is large, causing a high signal to be applied. This voltage on base 50 of transistor 52 will cause relatively large collector current flow through transistor to increase the voltage on base 5'6 of transistor 5E connected in cascade therewith. This increase in voltage on base 55d increases the llow of collector current through transistor 5S and through relay coil 96 in series therewith and it tends to attract balanced armature 4- causing it to rotate about its pivot and engage stationary contact $8 to cause the drive motor to move the antenna down or retract the same. At the same time the increased collector current through transistor S8 raises the voltage of emitter 'Til of this transistor. Since emitter 72 of transistor 7 4 is connected directly to emitter 7i) its voltage is simultaneously raised. The raising of the voltage at emitter 72 reduces the collector current of transistor 74 and in turn the current through relay Coil 9S. Thus as the main input signal at sensitivity adjustment increases the current through relay coil 96 increases and that through relay coil 98 decreases. This turns the armature 94 countercloclrwise about its pivot completing the circuit for stationary contact 92 and energizing the motor to retract the antenna.

As the antenna retracts the amplitude of the incoming signal will become smalleix resulting in a reduction in the ow of collector current through transistor 58 and an increase in the collector current of transistor 74 until such point as the fields of coil 96 and 93 balance and the armature 94 returns to balanced position. Ou the other hand,

L if at any time the amplitude of the signal applied to the receiver is not sutlicient to provide a listenable program, the voltage on base Sii of transistor' 52 falls below a predetermined point, reducing in turn the collector current of 5 transistor 58 and increasing the collector current through transistor 74. This unbalances the relay to rotate the armature 9d clockwise energizing the antenna motor to further extend the antenna and increase the signal applied to the receiver for unbalance. ln this way a balance 10 is maintained for a given desired signal strength and only as much antenna is extended as is required and not any in excess thereof.

As an alternative form of my invention, the sensitivity control may be made self compensating by connecting the adjustable contact dal to the motor drive so that as the motor operates to extend or retract the antenna as the need arises, it simultaneously moves the adjustable contact for correction in signal input. For example, if the signal strength of the incoming signal increases, the

relay is unbalanced to energize the motor in the down direction. Simultaneously, the motor would move the contact #i8 down to apply a smaller percentage of the sig- This provides a more quickly balanced system and one not so sensitive. En this system the adjustable contact dd would originally be located at the approximate center of resistance 42 and then adjust resistance 80 until the relay balances on a normal strength signal. After this interval adjustment the system will thereafter regulate itself automatically.

What is claimed is:

l. ln radio receiving apparatus, extensible antenna means, motive means mechanically connected to the exensible antenna means to either extend or retract the same, a source of electrical power, switching means interconrlccting said source of electrical power and said motive means to control energization of the same, amplifying means in said radio receiving apparatus connected to said extensibe antenna and receiving a signal therefrom of an intercepted modulated high frequency wave, means 4o connected Ito the amplifying means upon which a direct current voltage is developed which is proportional to the strength of the incoming high frequency wave intercepted by the antenna, and amplifying and control means connecting the means upon which a direct current voltage is developed and the switching means to actuate the same to cause the motive means to extend the antenna if the strength of the incoming wave decreases or retract the ante-nua if the strength of the incoming wave increases so that only the necessary amount of antenna will project beyond the housing.

2. In radio receiving apparatus, extensible antenna means, motive means mechanically connected to the extensible antenna means to either extend or retract the same, a source of electrical power, switching means interconnecting said source of electrical power and said motive means to control energization of the same, amplifying means in said radio receiving apparatus connected to said extensible antenna and receiving a signal therefrom of an intercepted modulated high frequency wave, means connected to the amplifying means upon which a direct current voltage is developed which is proportional to the strength of the incoming high frequency wave intercepted by the antenna, transistorized amplifying means connected to the means upon which a direct current voltage is developed proportional to the incoming wave and having a plurality of paths through which current flow, the current through one path increasing as the voltage proportional to the signal wave increases and that through the other path simultaneously decreasing and vice versa and switch operating means electrically connected to the transistorized amplifying means to operate the switching means and cause the motive means to run in one direction if the voltage developed proportional to the signal wave increases and in the opposite direction if it decreases to raise and lower the antenna as the signal strength varies.

3. ln radio receiving apparatus having an extensible antenna and high frequency amplifying means, impedance means in the high frequency amplifying means upon which a direct current voltage is developed upon receipt of an incoming signal which voltage is proportional to the strength of the signal, a reversible motor mechanically coupled to the extensible antenna to raise and lower the same, switching means connected to the reversible motor to control the same, balanced relay means mounted in juxaposition to the switching means and connected thereto to actuate the same and cause the reversible motor to run in one direction or the other, and amplifying means connected to the impedance means upon which a direct current voltage is developed and to the balanced relay means to control the reversible motor to raise or lower the antenna with variations in input signal strength.

4. In radio receiving apparatus having an extensible antenna and high frequency amplifying means, impedance means in the high frequency amplifying means upon which a direct current voltage is developed upon receipt of an incoming signal which voltage is proportional to the strength of the signal, a reversible motor mechanically coupled to the extensible antenna to raise and lower the same, switching means connected to the reversible motor to control the same, balanced relay means mounted in juxtaposition to the switching means and connected thereto to actuate the same and cause the reversible motor to run in one direction or the other, a pair of transistors connected to the impedance means upon Which a direct current voltage is developed and to the balanced relay and so coupled that as the current flow through one transistor increases the current flow through the other decreases with change in voltage developed on the impedance means to so control the reversible motor to raise and lower the antenna as the signal strength changes.

No references cited. 

